Magnetostrictive transmitter



Sept. 17, 1935. s. w. PIERCE 2,014,412

MAGNETOSTRICTIVE TRANSMITTER I Original Filed July 20. 1928 2 Sheets-Sheet l Sept. 17, 1935. ca. w. PIERCE 2,014,412

me'r'w'rosrrnrcmvn TRANSMITTER I v v 1 Original Filed July 20, 1928 2 Sheets-Sheet 2 6'e eWEzJerca QMM Patented Sept,. 17, 1935 UNITED STATES PATENT OFFICE.

Divided and this application November 19, 1930, Serial No. 496,809. In Canada December 31, 1927 Claims. (01. 177-386) The present invention relates to the transmission of intelligence, using sound as the'agency of communication, and more particularly to communication by sound through water or other 5 dense media. The present application is filed in response to requirements for division made by the Patent Ofllce. in application Serial No; 294,288, filed July 20, 1928, andin the parent application of the same, Serial No. 158,452, filed January 3,

1927, which matured, on March 11, 1930, into Letters Patent No. 1,750,124. i

A feature of the invention is the use of tun magnetostrictive vibrators. Magnetostrictive vibrators are constituted of a magnetostrictive core disposed in an electromagnetic field, such as may be produced by a coil or winding in an electric circuit. when stimulated magnetically by the field, the core becomes slightly mechanically de-. formed or distorted by magnetostriction. The resuiting increment of deformation may be a lengthening, or a shortening, or some other dis- 95 ings, in which Fig. 1 is a diagrammatic view of apparatus and circuits constructed and arranged to illustrate a principle of the present invention; Fig. 2 is a sec on of a vibrator particularly designed for pro cing sound in water, the section it! beingtaken upon the line 2-2 of Fig. 3, looking in the direction of the arrows; Fig. 3 is an elevation of the same; Figs. 4 and 5 are views similar to Figs. 2 and 3, respectively, of a. modification;

Fig. 6 is a diagrammatic cross section of a ship, 45 showing a vibrator spanning the hull thereof; and

Fig. 7 is a diagrammatic view of a transmittingand-receiving system accordingto the present invention, it being understood that either end of the system may be operated either to transmit or to- 60 receive.

A core 2 isshown in Fig. 1 axiallypositioned in and driven by an inductive field solenoid coil 1 IO. The core 2 is shown in Fig. 1 held in place by means of two centrally positioned clamps i and I! 0 so as freely to vibrate longitudinally about a nodal point at its center. The core 2 may bein the form of a tube, or a rod, or it may be otherwise constructed, as explained in the said Letters Patent. As is also described in the said Letters Patent, it is preferably of nickel, nickel-steel, nickelii copper, nickel-cobalt, chrome-nickel, chrome steel, or of any other metal element or alloy char acterized by comparatively large magnetostrictive effects and comparatively low vibrational decrement. By proper choice of length and other di- 10 The coil I0 is provided with conductors l2 and l5 H by which it may be connected, for simplicity, in series with a source of alternating electromotive force, such as an altematlng current generator ,l6, for passing an actuating period current through the coils I0. Other, more complicated, 2c sourcesof alternating current are illustrated in other figures of the above-entitled Letters Patent.

A local battery iii, in series with the source it and the winding Ill, applies a steady magnetizing field to the core 2, over which the alternating field produced by the generator I6 is superposed, so as to poiarize the core}. A similar polarizing battery is shown at 93 in Fig. 'l. The electrical circuit thorugh the energizing coils should preferably be tuned, as by. the condenser 92, in order, to obtain maximum driving current through the coils. The alternating field is preferably smaller than the steadyfield; in order that the combined fields, may not, at any time, fall to zero. The battery may be dispensed with, and the core may be magnetized electromagneticaliy by a local source, or it may be permanently magnetized, instead, or the battery and a permanently magnetized core may beemployed together.

' If the current or voltage is alternating, the 40' electromagnetic field created thereby will also be A alternating. The core 2 will. therefore increase and decrease in length (let us say) many times a second, everyjvariation in the current producing its stimulative 'eflect on the core 2, and every 5 deformation of the core producing its reaction response upon the current. .The' core 2 will, in

Iconsequence, vibrate mechanically by magnetoof vibration of the'core, though still small, becomes relatively quite large. then react inductively on the load to render its consumption of power critical as to frequency for frequencies near the free frequency of the core. By proper choice of' length and other dimensions, as before stated, the cores 2 may be proportioned effectively to transmit vibrational stresses lengthwise of the cores 2 to and from the hereinafter. The mechanical described diaphragm means. damping of the core, mounted as shown, may be made small, with the result that the resonant response of the core is very sharp and pronounced. Of course, there will usually be more than one specific frequency of magnetization at which the core will thus resonate; for in addition to one or more natural fundamental frequencies of mechanical vibration, it has also frequencies of vibration determined by the operation of the core in halves, thirds, fourths, fifths, etc., as is explained more at length in the said Letters Patent, and it will be sufiicient here to remember that the operation described herein is equally applicable to the fundamentals and their overtones.

According to the present invention, the magnetostrictive core isadapted, as a sonic oscillator, for the production of sounds of any desired frequency, particularly high frequencies, for sonorously communicating through water or other dense media. One or more cores 2, of highly magnetostrictive material, are shown attaced to one or more diaphragms 58, Figs. 2 to 5, positioned in the water or other medium. The diaphragms have restricted areas, as shown, to which their sonorous vibration is confined. ,The cores 2 are surrounded by coils 22 that may be connected together, either in parallel or in series, as desired, and through which are passed an actuating periodic current superposed over a magnetizing direct current, as before described. The fields of adjacent coils may be reversed, so that the lines of force may go to the right through one set of cores 2 and to the left through the alternately placed set of cores 2. When sharply resonant operation at a single frequency is desired, the

magnetizing current may be passed through auxiliary coils, if desired. The cores are preferably free from contact with the coils, so as to reduce friction, which would prevent free vibration. The mechanical system is tuned to the desired frequency, in the medium in which it is to be used. thus, enormously increasing, with the electrical tuning, the radiation of sound from the transmitter. The diaphragm means and its cores 2 may be so designed as to elasticity, length and other dimensions, and associated mass, as to have, as a unit, a natural period of mechanical vibration resonant to the frequency of the periodic current in the coils 22. In some cases, it

may be desirable to utilize one vibratory transmitter at a number of frequencies in a given frequency range. For such purposes, it will be desirable to broaden the resonance curve of the mechanical vibrator by the introduction of mechanical damping, so as to increase the response of the vibrator to frequencies removed from its resonant frequency. J

The diaphragm means and its cores 2*may be so designed as to elasticity, length and other dimensions, and associated mass. as to have, as a unit, a, natural period of mechanical vibration resonant to the frequency of the periodic current in the coils 22. The chamber in' which the coils are contained is sealed against the entry of water The core 2 will' The magnetostrictive vibrators are thus con- 10 stituted of a plurality of magnetostrictive bodies separately dimensioned for resonantly cooperating with the diaphragm means, in their expansion and contraction, to interchange energy with the sound-conveying medium. By their magneto- 15 -strictive expansion and contraction, under the action of currents'in the coils 22, the cores 2 will cooperate with the coils 22 to vibrate the diaphragm means to produce radiation of sound into the medium. By their expansion and con- 20 traction in response to the incidence of sound in the medium upon the diaphragm means, the cores 2 will cooperate with the coils 22 to generate electric voltages in the coils 22. Alternatively, the

single diaphragm 58 may be utilized as the radl- 25 ating surface, in which case the caps 62 are dimensioned to act eifectively as an inertia load on the cores to adapt the vibrations of the device to the mechanical characteristics of the medium in which it is used. The diaphragms as may be square, as illustrated, or they may be circular or rectangular. The driving cores are preferably distributed over a substantial portion of the diaphragm surface. A multiple unit of this character will produce greater powerthan a single unit of corresponding area, and is freer from eddy-current and hysteresis losses, besides being more flexible, so as more easily to conform elastically to the nature of the medium in which it is operating. The number of magnetostrictive elements, their distribution and their lengths are of .magnitudes suitable to easy adjustment for at prede ermined resonant system designed to operate at any given frequency, within a wide range as, for .example, 10,000 or- 40,000 cycles per sec- 0nd. The distribution of driving members-per; mits the ready radiation and distribution of heat, and lends itself to the use of large amounts of power. With thirty seven magnetostrictive driving elements, more than a kilowatt of power can be supplied to the system at 30,000 cycles per second; and, by a large number of elements, proportionally larger power may be .used. The mul tiple-driven diaphragm is elastically supported at properly spaced distributed areas, capable of 5 sharp and effective tuning, with a large radiat ing face, and the system has low, mechanical internal-power losses, capable of high rigidity, or of a rigidity adaptable to the medium in which it is used, by the choice of areas and distribution of driving elements. The system is also .characterized by great durability, constancy, and high efilciency The magnetostrictive drive produces an elasticity and rigidity determined in large part by the driving cores themselves. A distribution of these members over the face of the diaphragm supplies rigidity to it at a multitude of points and insures a more uniform elasticityfor the whole radiating diaphragm.

According to the modification or Fig. 6, the

magnetostrictiv core 2 is'attached to the inner opposite sides 64 and 06 of a ship. These sides will themselves act as sound radiators through the water when properly tuned, alternating current is sent through the coils 22. The system is particularly effective when the vibrator is connected in circuit with an amplifier. Here the frequency will be low, as for audible signalling. As before explained, the magnetostrictive element should be polarized by a direct-current battery, or through an auxiliary winding. For certain frequencies, as at 1,000 cycles, the core may be directly driven, as by the generator It. If desired,

it may be driven by a vacuum tube, as illustrated in Fig. 7, or by other vacuum-tube apparatus, such as a power amplifier. The vibrator attached to the ship may, of course, be of .the forms illustrated in Figs. 2 to 5. To get the maximum am- 1 plitude of the previously designed vibrator, the

or anode 28, is provided with a-coil 16 that is coupled to a coil I8. The grid is shown at 32. The coil 18 is connected in circuit with a tuning condenser 92 and the energizing coil 8| ofv a suit- -ably oriented, magnetostrictive vibrator 00. The

' vibrator 80 may be polarized by 'a parallel feed consisting of a source 93 of direct or altemating 'potential, and containing a choke coil 94 for confining the oscillatory current to the circuit containing the. energizing coil- 8L] The energy with a telephone 90.

of the vacuum tube 14 is thus magnetostrictively transmitted to the sound-radiating vibrator 80, which may be of the form disclosed in Figs. 2 to 5; and it may, in fact, be the vibrator 2 of Fig. 6. The sound so radiated is received by a suitably oriented, sound-receiving vibrator 82 of a receiving system. The energizing coil 83 of the vibrator- 82 is connected in circuit with a tuning condenser 85 and a coil 8!, a choke coil 91 and a potential source 99 being provided similar to the elements 94 and 93. The coil 84 is coupledto a coil 86 of a receiving vacuum tube that is connected Additional tuning condensers 98 and I00 may be employed for the transmitter and thereceiver. The generator and associated parts will, as before, electrically phragm means, so that the system shall be directively discriminating as to the sound, thus rendering the diaphragm means directive. Instead of the inductive coupling shown in Fig. 7, other methods of coupling used in related arts may be employed.

It will readily be understood, without further description, that the coils of a single vibrator may be connected either to a transmitting or a receiving apparatus, as by means of suitable switching arrangements and, indeed; that each such apparatus may, in itself, be used-eitheras a sending or a receiving apparatus. wlllbeobvioustopersonsskilledinthe'art,and

.ment of the diaphragm means to produce sub- Other modifications, too,

. all such are considered to fall within the spirit and scope of the present invention, as, defined in the app nded claims.

What is claimed is:

l. A frequency-discriminating sound transmitter having, in combination, a mechanical vibratory system comprising diaphragm means adapted to be positioned in relation to a soundconveying medium to produce radiation of sound into the medium by means of its sonorous vibra- 10 tion, and core means of highly magnetostrictive material aiiixed to the diaphragm means, coil means for magnetizing the core means, the crosssectional area of the metal of the core means being small relative to the area of the diaphragm 15 means, but the'core'means being proportioned,

and distributed over the surface of the diaphragm means, effectively to transmit vibrational stresses "lengthwise of the core means to and from the diaphragm means in order to enable the core means 20 to cooperate with the coil means, by its'magnetostrictive expansion and contraction under the actionof currents in the coil means, to vibrate the diaphragm means, and a source ofcurrents of pre determined frequency higher than speech fre-Bliquencies connected with 'the coil means, the source of currents being of sufliciently high power and the coil means having suflicient current-carrying capacityto effect suflicient vibratory movestantial radiation of sound into the medium, and the source of currents being selective as to frequency, to produce vibratory magnetostrictive expansion and contraction of the core means at the said predetermined frequency.

2. A frequency-discriminating sound transmitter having, in combination, a mechanical vibratory system comprising diaphragm means adapted to be positioned in relation to a soundconveying medium to produce radiation of sound 40 sectional area'of the metal of the core means be- 45.

ing small relative to the area of the diaphragm means, but the core means being proportimied,

and distributed over'the surface of the diaphragm means, eifectively to transmit vibrational stresses lengthwise of the core means to and from the 50 diaphragm means in order to enable the core means to cooperate with the coil means, by its" magnetostrictive expansion and contraction under the action of currents in the coil means, to vibrate the diaphragm means, a source of currents 55 of predetermined frequency higher than speech frequencies connected with the coil means, the source of currents being of suificiently high power and the coil means having suiiicient current-car Y rying capacity to effect sufficient vibratory movee 00 ment of the diaphragm means to produce'substantial radiation of sound into the medium, the source of currents being selective. as to frequency; to produce vibratory magnetostrictive expansion and contraction of the core means at the said pre-' as determined frequency, the core means being (11- mensioned and tuned to cooperate effective in its vibration with the currents of the said rede-' tcrmined frequency, and meansfor adjusting the predetermined frequency of the mechanical 3. A frequency-discriminating sound-transmitter having, in combination, a mechanical vibratory system having a natural period of vibration and comprising adiaphragm adapted to be pouency into resonanc e with the dimensions of values to causethe. diaphragm and i the core means both to contribute substantially to the said natural period of vibration of the mechanical system, the vibrational constants and spatial distribution of the core means cooperating with the diaphragm forces tofacilitate piston-wise cophasing of the parts of the diaphragm atthe said efiective wave length, coil means for magnetizing the core means, the cross-sectional area of the metal of the core means being small relay tive to the area of the diaphragm, but the core means being proportioned, and distributed over the surface of the diaphragm, effectively to transmit vibrational stresses lengthwise of the core means to and from the diaphragm in order to enable the core means to cooperate with the coil means, by its magnetostrictive expansion and contraction under the action of clu'rents in the coil means, to vibrate the diaphragm piston-wise, and a source of currents of predetermined frequency higher than speech frequencies connected with the coil means, the source of currents being of suin'ciently high power and the coil means having suflicient current-carrying capacity to effect sufiicient vibratory movement of the diaphragm means to produce substantial radiation of sound into the medium, and the source being selective as to frequency, to produce vibratory magnetrostrictive expansion and contraction of the core means at the said predetermined high frequency.

4. A frequency-discriminating sound transmitter. having, in combination, a mechanical vibratory system comprising diaphragm means adapted to be positioned in relation to a sound-conveying medium to produce radiation of sound into the medium by means of its sonorous vibration, and core means of highly magnetostrictive ,material affixed to the diaphragm means, coil means ,for magnetizing the core means, the cross-sectional area of the metal of the core means being small relative to the area of the diaphragm means. but the core means being proportioned, and distributed over the surface of the diaphragm means,

efl'ectively to-transmit vibrational stresses lengthwise of the core means to and from the diaphragm 5 'coil means with the output circuit, the vacuumtube source being selective as to frequency, to 15 produce vibratory magnetostrictive expansion and contraction of the core means at the said predetermined frequency.

5 A frequency-discriminating sound transmitter having, in combination, a mechanical vibra- 20 tory system comprising diaphragm means adapted to be positioned in relation to asound-conveying medium to produce radiation of sound into the medium by means of its sonorous vibration, and core means of highly magnetostrictive material 25 amxed to the diaphragm means,'coil means for magnetizing the core means, the cross-sectional area of the metal of the core means being small relative to the area of the diaphragm means, but the core means being magnetically polarized and 30 proportioned, and distributed over the surface of the diaphragm means, efiectively to transmit vibrational stresses lengthwise of the core means to and from the diaphragm means in order to enable the core means to cooperate with the coil means, by its magnetostrictive expansion and contraction under the action of currents in the coil means, to vibrate the diaphragm means, and a sourceof currents of predetermined frequency .higher than speech frequencies connected with the coil means, the source of currents being of sufllciently high power and the coil means having suflicient current-carrying capacity to eifectsufilcient vibratory movement of the diaphragm means to produce. substantial radiation of sound 4 into the medium, and the source of currents being selective as to frequency, to produce vibratory magnetostrictive expansion and contraction of the core means at the said predetermined frequency.

' GEORGE W. PIERCE. 

